1. Field of the Invention
The present invention relates to electronic apparatuses and methods for detecting a hazard for movement. More specifically, the present invention relates to an electronic apparatus having, for example, a movable face for opening and closing a slot for loading a recording medium or the like.
2. Description of the Related Art
In conventional on-vehicle audio/visual devices (e.g., navigation apparatuses) of a known type, behind a rotatable operation panel (hereinafter referred to as a movable face) having keys and a display, a medium loading slot for loading an information recording medium is provided so that a wide space for display is provided. Regarding the on-vehicle devices of the type described above, when an information recording medium is provided to the on-vehicle device, the movable face is rotated to expose the medium loading slot, and a medium such as a compact disk (CD), a digital video disk (DVD), a mini disk (MD), or a cassette tape is provided to the on-vehicle device through the medium loading slot, the movable face is then moved back to the original position, and then information is played back from or is recorded on the information recording medium.
FIGS. 13A to 13C show schematic constructions of movable faces according to the related art. Referring to FIG. 13A, a movable face 901 is allowed to slide and rotate in the direction of an arrow from a front surface of an apparatus 900 so that a medium loading slot 902 is exposed or hidden as appropriate. Referring to FIG. 13B, a movable face 911 is closed or opened in the direction of an arrow about a rotation axis (not shown) on a front surface of an apparatus 910 so that a medium loading slot 912 is exposed or hidden as appropriate. Referring to FIG. 13C, a movable face 921 is horizontally moved from a front surface of an apparatus 920 and then rotated so that a medium loading slot 922 is exposed or hidden as appropriate.
When an unexpected object gets into and is pinched by a mechanism for moving the movable face, even when a motor is driven, the movable face is not moved in a desired direction. This could lead to a serious problem, such as damage to the motor or damage to other parts of the mechanism. Thus, in a conventional device having a movable face, a switch for detecting an open state of the movable face and a switch for detecting a closed state of the movable face are provided, and it is determined that an unexpected object is pinched or abutted when a switch is not turned on within a predetermined time, and the movable face is protected, i.e., the movable face is stopped or the direction of movement of the movable face is reversed. Also, a method that does not employ detection switches has been proposed. According to the method, the current of a driving motor for moving the movable face is detected, and when a current exceeding a predetermined amount is detected, it is determined that an unexpected object is pinched or abutted and the face is protected.
According to the conventional method, however, time is set with detection switches provided at a start point and an end point of movement of the movable face, so that the movable face is not protected until the predetermined time elapses, sometimes resulting in a serious problem. According to the conventional method that detects an excess current, it is difficult to accurately determine whether the load is actually caused by the movable face or the load is caused by pinching of an unexpected object. Thus, in some cases, the movable face is erroneously protected, or a serious problem occurs without protecting the movable face.
As techniques for overcoming these problems, for example, a method of detecting a hazard for movement, disclosed in Japanese Unexamined Patent Application Publication No. 2000-155018, is known. According to this method, the position of a movable member after elapse of a predetermined time from a current time is predicted, and whether a hazard for movement has occurred is determined based on whether the movable member has passed the predicted position when the predetermined time has elapsed.
According to the method disclosed in Japanese Unexamined Patent Application Publication No. 2000-155018, however, the speed of movement of the movable member is constant from a retracted state to an extended state, and a period for determining whether a hazard for movement has occurred is also constant. Thus, quick operation is not allowed even when the probability of occurrence of a hazard is extremely low, for example, in an initial stage of moving from the retracted state to the extended state or an initial state of moving from the extended state to the retracted state.